1. Field
Some example embodiments of the present disclosure may relate to sensorless control apparatuses and/or control methods thereof. Some example embodiments may relate to sensorless control apparatuses capable of sensing rotors being out of orientation in sensorless controls of electric motors and/or a control methods thereof.
2. Description of Related Art
An electric motor is an apparatus configured to convert electric energy into mechanical energy by use of a force applied to a conductor with flowing electric current in a magnetic field. The electric motor may be a direct current motor or an alternating current motor depending on the type of power being used. The alternating current motor may be a one phase alternating motor or a three phase alternating motor. Each alternating current motor may be an induction-type motor or a synchronous-type motor.
The synchronous motor may be supplied with a magnetic flux from a permanent magnet attached on a rotor and, at all times, precise position information of the rotor may be needed to perform vector control. In order to obtain the position information of the rotor, a position detection sensor, such as a resolver or an encoder, may need to be attached to a shaft of the motor. However, the position detection sensor is expensive, and requires additional complicated hardware. In addition, having the position detection sensor mounted on the shaft of the motor increases the size of the motor and the weight of the motor.
In order to remove the constraints as such, a large amount of research has been conducted on sensorless control. Sensorless control refers to a control scheme to obtain the position of a rotor in an indirect manner without using a position detection sensor.
Since the sensorless control does not have a position detection sensor, an occurrence of being out of orientation is difficult to sense. If electric current is continuously supplied to a motor for a control operation in a state of being out-of-orientation, the motor may break down due to excessive current.
The conventional sensorless control may use an out-of-step detection scheme in which a speed command is provided to a motor and, after a predetermined period of time, if the motor fails to reach to a target speed, the motor is determined to be out-of-orientation. However, the out-of-step detection as such is not suitable for a case having a variable load torque or a case that does not require precise speed control. In addition, even if the rotor does not rotate in practice, a sensorless algorithm may have abnormal operation that erroneously estimates the rotor as being rotated.